Edelbrock StepUp Springs w/ 20 vacuum

About the car 65 Valiant Conv:
Low mileage 318 rebuilt by previous owner, but assume mild cam and compression below 9, standard 318 heads (but do not have exact specs). 1406 carb and streetmaster intake. 904 auto. No power breaks.

Question: The set of 1406 setup springs only goes to 8 Hg, which you half, but my vacuum at idle is 20 Hg / 700 rpm idle. Should I be worried that 20 is oddly high and/or I should have an even heavier spring?

The car doesn't stutter at mild to heavy acceleration going from 1st to 2nd gear, so maybe I'm just worrying too much, but always wonder if things could be better.

I like to bring a vacuum guage inside the car and monitor the vacuum in high gear and a light load at cruising speed 55-60. Then start jetting down a couple thousandths at a time until a lean surge develops. Then jet back up a couple thousandths. Now you’ll want the springs to give you enrichment just below the cruise vacuum that you noted earlier. You can stretch the heaviest spring and or add an ink pen spring inside the original spring. Whatever it takes. This will make your engine crisp. In fact if you drive in the winter you may have to put a richer metering rod in to help out a cold engine.

Use the strongest spring in the kit, job done.